The present invention relates to a toroidal type continuously variable transmission (CVT), and more particularly to a dual cavity toroidal type CVT.
A dual cavity toroidal type CVT is known from JP-A 11-63139. FIG. 6 is a schematic view of the known CVT. Referring to FIG. 6, the CVT includes two toroidal transmission units 2, which include coaxial front and rear input discs 2a, a common output disc 2b, and power rollers 2c. An output gear 5 is fixedly attached to output disc 2b. Among power rollers 2c, two are interposed between front input disc 2a and output disc 2b, while the other two between rear input disc 2a and output disc 2b. A sleeve 3 passes through a central bore of output disc 2b and carries front and rear input discs 2a for a unitary rotation. A shaft 6 extends through sleeve 3. Via shaft 6, rotation of a crankshaft of an engine 1 is transmitted to a loading cam 4. Loading cam 4 drives rear input disc 2a. 
JP-A 1-193454 discloses a structure for supporting two output discs of a dual cavity toroidal type CVT. According to this known supporting structure, a transmission casing has an integral support wall. The support wall extends into a space between the output discs. Radial and thrust bearings are interposed between the support wall and the output discs. Via these bearings, the support wall supports the output discs against radial and thrust loads.
JP-A 6-307514 discloses a structure for supporting two output discs of a dual cavity toroidal type CVT. In this known structure, a stationary sleeve is fixedly attached to a transmission casing by posts. This sleeve supports the two output discs via radial bearings. A shaft extends through the sleeve and carries two axially spaced input discs for a unitary rotation.
JP-A 11-51136 discloses a structure to support a shaft against radial and thrust loads. The shaft extends through a sleeve and central bores of two output discs. The output discs are fixedly attached to one and opposite end portions of the sleeve. An output gear is disposed between the output disc and formed integral with the sleeve. Via radial bearings, the shaft supports the output discs. Two spaced supports have radial bearings, respectively, to support the shaft against radial load. A support wall of a transmission casing has a ball bearing to support the shaft against thrust load. In another example, two spaced supports have ball bearings, respectively, to support the shaft against not only radial load but also thrust load,
JP-A 5-126222 discloses a dual cavity toroidal type CVT. In this known CVT, an output shaft carries two spaced output discs for a unitary coaxial rotation. Two input discs are fixedly coupled to a sleeve through which the output shaft extends. Loading cams are interposed between the two input discs.
The known toroidal type CVTs are satisfactory to some extent. However, a need remains for development of a dual cavity toroidal type CVT employing a common output disc having a peripheral output gear. Such toroidal type CVT has a problem that thrust load applied to a common output disc from the output gear tends to tilt the disc from a predetermined normal upright position thereof.
An object of the present invention is to provide a toroidal type CVT having a structure to cope with thrust load tending to tilt a disc from a predetermined normal upright position thereof.
Another object of the present invention is to provide an easy to assemble structure to cope with thrust load tending to tilt a disc.
According to one aspect of the present invention, a toroidal type continuously variable transmission (CVT) comprises:
two toroidal transmission units having a first disc, a second disc, a third disc, and a torque delivery shaft carrying the first and second discs coaxially for a unitary rotation therewith,
the third disc being a common disc to the first and second discs and disposed between the first and second discs in operative cooperation therewith,
the third disc having a peripheral gear and a central bore through which the torque delivery shaft extends, the third disc having a wall defining the central bore;
at least one radial bearing in rolling contact with the central bore defining wall and the torque delivery shaft for allowing a rotational displacement between the third disc and the torque delivery shaft; and
supports interposing therebetween the third disc to bear thrust load tending to tilt the third disc from a predetermined position to hold the third disc in the predetermined position.